There are already known in the art dental X-ray diagnostic devices provided with an X-ray radiator exterior to the patient and a film holder to be introduced into the mouth of the patient, and means for determining the exposure time. It is already known how to use a timer switch or an mAs relay for setting the exposure time.
A timer switch or an mAs relay must be set by hand in order to determine the exposure time. The operator must estimate and set the required exposure time or the required mAs product on the basis of the patient's condition. Faulty exposures are possible. Therefore, with the trend toward automation, it is desirable to automatically set the exposure time for a dental X-ray diagnostic device, i.e., to use an automatic exposure circuit.
It is, therefore, an object of the present invention to provide a dental X-ray diagnostic device for the preparation of X-ray film pictures, with an X-ray radiator exterior to a patient and a film holder which can be introduced into the mouth of the patient, and means for measuring and setting the exposure time which contains a switching device for switching off the X-ray tube high voltage upon reaching the dosage corresponding to the optimum film blackening.
Another object of the present invention is to provide a dental X-ray diagnostic device of the foregoing character in which this device comprises an automatic exposure circuit for setting the exposure time whose individual parts bother neither the operator nor the patient during operation.
A further object of the present invention is to provide an X-ray diagnostic device, as described, which may be economically fabricated and which has a substantially long operating life.